4 use errors::Applicability;
8 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
9 use rustc::hir::itemlikevisit::ItemLikeVisitor;
10 use rustc::hir::print::visibility_qualified;
12 use rustc::util::nodemap::DefIdSet;
14 use rustc_data_structures::fx::FxHashMap;
16 pub fn check_crate(tcx: TyCtxt<'_>) {
17 let mut used_trait_imports = DefIdSet::default();
18 for &body_id in tcx.hir().krate().bodies.keys() {
19 let item_def_id = tcx.hir().body_owner_def_id(body_id);
20 let imports = tcx.used_trait_imports(item_def_id);
21 debug!("GatherVisitor: item_def_id={:?} with imports {:#?}", item_def_id, imports);
22 used_trait_imports.extend(imports.iter());
25 let mut visitor = CheckVisitor { tcx, used_trait_imports };
26 tcx.hir().krate().visit_all_item_likes(&mut visitor);
28 unused_crates_lint(tcx);
31 impl ItemLikeVisitor<'v> for CheckVisitor<'tcx> {
32 fn visit_item(&mut self, item: &hir::Item) {
33 if item.vis.node.is_pub() || item.span.is_dummy() {
36 if let hir::ItemKind::Use(ref path, _) = item.node {
37 self.check_import(item.hir_id, path.span);
41 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
44 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {
48 struct CheckVisitor<'tcx> {
50 used_trait_imports: DefIdSet,
53 impl CheckVisitor<'tcx> {
54 fn check_import(&self, id: hir::HirId, span: Span) {
55 let def_id = self.tcx.hir().local_def_id_from_hir_id(id);
56 if !self.tcx.maybe_unused_trait_import(def_id) {
60 if self.used_trait_imports.contains(&def_id) {
64 let msg = if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
65 format!("unused import: `{}`", snippet)
67 "unused import".to_owned()
69 self.tcx.lint_hir(lint::builtin::UNUSED_IMPORTS, id, span, &msg);
73 fn unused_crates_lint(tcx: TyCtxt<'_>) {
74 let lint = lint::builtin::UNUSED_EXTERN_CRATES;
76 // Collect first the crates that are completely unused. These we
77 // can always suggest removing (no matter which edition we are
79 let unused_extern_crates: FxHashMap<DefId, Span> =
80 tcx.maybe_unused_extern_crates(LOCAL_CRATE)
82 .filter(|&&(def_id, _)| {
83 // The `def_id` here actually was calculated during resolution (at least
84 // at the time of this writing) and is being shipped to us via a side
85 // channel of the tcx. There may have been extra expansion phases,
86 // however, which ended up removing the `def_id` *after* expansion such
87 // as the `ReplaceBodyWithLoop` pass (which is a bit of a hack, but hey)
89 // As a result we need to verify that `def_id` is indeed still valid for
90 // our AST and actually present in the HIR map. If it's not there then
91 // there's safely nothing to warn about, and otherwise we carry on with
94 // Note that if we carry through to the `extern_mod_stmt_cnum` query
95 // below it'll cause a panic because `def_id` is actually bogus at this
96 // point in time otherwise.
97 if let Some(id) = tcx.hir().as_local_hir_id(def_id) {
98 if tcx.hir().find(id).is_none() {
104 .filter(|&&(def_id, _)| {
105 tcx.extern_mod_stmt_cnum(def_id).map_or(true, |cnum| {
106 !tcx.is_compiler_builtins(cnum) &&
107 !tcx.is_panic_runtime(cnum) &&
108 !tcx.has_global_allocator(cnum) &&
109 !tcx.has_panic_handler(cnum)
115 // Collect all the extern crates (in a reliable order).
116 let mut crates_to_lint = vec![];
117 tcx.hir().krate().visit_all_item_likes(&mut CollectExternCrateVisitor {
119 crates_to_lint: &mut crates_to_lint,
122 for extern_crate in &crates_to_lint {
123 let id = tcx.hir().as_local_hir_id(extern_crate.def_id).unwrap();
124 let item = tcx.hir().expect_item(id);
126 // If the crate is fully unused, we suggest removing it altogether.
127 // We do this in any edition.
128 if extern_crate.warn_if_unused {
129 if let Some(&span) = unused_extern_crates.get(&extern_crate.def_id) {
130 let msg = "unused extern crate";
132 // Removal suggestion span needs to include attributes (Issue #54400)
133 let span_with_attrs = tcx.get_attrs(extern_crate.def_id).iter()
134 .map(|attr| attr.span)
135 .fold(span, |acc, attr_span| acc.to(attr_span));
137 tcx.struct_span_lint_hir(lint, id, span, msg)
138 .span_suggestion_short(
142 Applicability::MachineApplicable)
148 // If we are not in Rust 2018 edition, then we don't make any further
150 if !tcx.sess.rust_2018() {
154 // If the extern crate isn't in the extern prelude,
155 // there is no way it can be written as an `use`.
156 let orig_name = extern_crate.orig_name.unwrap_or(item.ident.name);
157 if !tcx.extern_prelude.get(&orig_name).map_or(false, |from_item| !from_item) {
161 // If the extern crate is renamed, then we cannot suggest replacing it with a use as this
162 // would not insert the new name into the prelude, where other imports in the crate may be
164 if extern_crate.orig_name.is_some() {
168 // If the extern crate has any attributes, they may have funky
169 // semantics we can't faithfully represent using `use` (most
170 // notably `#[macro_use]`). Ignore it.
171 if !tcx.get_attrs(extern_crate.def_id).is_empty() {
175 // Otherwise, we can convert it into a `use` of some kind.
176 let msg = "`extern crate` is not idiomatic in the new edition";
178 "convert it to a `{}`",
179 visibility_qualified(&item.vis, "use")
181 let base_replacement = match extern_crate.orig_name {
182 Some(orig_name) => format!("use {} as {};", orig_name, item.ident.name),
183 None => format!("use {};", item.ident.name),
185 let replacement = visibility_qualified(&item.vis, base_replacement);
186 tcx.struct_span_lint_hir(lint, id, extern_crate.span, msg)
187 .span_suggestion_short(
191 Applicability::MachineApplicable,
197 struct CollectExternCrateVisitor<'a, 'tcx> {
199 crates_to_lint: &'a mut Vec<ExternCrateToLint>,
202 struct ExternCrateToLint {
203 /// `DefId` of the extern crate
206 /// span from the item
209 /// if `Some`, then this is renamed (`extern crate orig_name as
210 /// crate_name`), and -- perhaps surprisingly -- this stores the
211 /// *original* name (`item.name` will contain the new name)
212 orig_name: Option<ast::Name>,
214 /// if `false`, the original name started with `_`, so we shouldn't lint
215 /// about it going unused (but we should still emit idiom lints).
216 warn_if_unused: bool,
219 impl<'a, 'tcx, 'v> ItemLikeVisitor<'v> for CollectExternCrateVisitor<'a, 'tcx> {
220 fn visit_item(&mut self, item: &hir::Item) {
221 if let hir::ItemKind::ExternCrate(orig_name) = item.node {
222 let extern_crate_def_id = self.tcx.hir().local_def_id_from_hir_id(item.hir_id);
223 self.crates_to_lint.push(
225 def_id: extern_crate_def_id,
228 warn_if_unused: !item.ident.as_str().starts_with('_'),
234 fn visit_trait_item(&mut self, _trait_item: &hir::TraitItem) {
237 fn visit_impl_item(&mut self, _impl_item: &hir::ImplItem) {